In an OFDM system, all the subcarriers are summed after an IFFT (Inverse Fast Fourier Transform, IFFT) operation, so a transmitted signal in the time domain will have a very high peak value. Therefore, compared with a single-carrier system, the OFDM system has a very high peak to average power ratio (Peak to Average Power Ratio, PAPR). In fact, the high PAPR not only reduces the efficiency of a transmitter power amplifier but also reduces the signal to quantization noise ratio (Signal to Quantization Noise Ratio, SQNR) of an analog to digital converter (Analog to Digital Converter, ADC) and a digital to analog converter (Digital to Analog Converter, DAC), so it is one of the most unfavorable factors in the OFDM system.
A low peak to average ratio sequence is very important and is widely used in an OFDM communication system. For example, the sequence with a low PAPR can be used as a channel estimation training field in a preamble. A transmitting end transmits the sequence with a low PAPR, and since the sequence with a low PAPR is unlikely for distortion in a transmission process, a receiving end can carry out channel estimation. Theoretical studies also indicate that sequence with low PAPRs usually have excellent autocorrelation performance, which is also a very important advantage in the OFDM wireless communication system.
At the same time, there are many restrictions on the generation of traditional sequence with low PAPRs. For example, constant envelope zero correlation sequences adopted in the LTE, such as a Zadoff-Chu sequence can only get a good PAPR performance at some lengths, and the generated sequence elements are different complex numbers, thereby increasing the implementation complexity.